Thesis (MScMedSc (Pathology. Medical Virology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: In 2007, AIDS caused an estimated 2.1 millions deaths worldwide; about 70% in sub-Saharan Africa. HIV preferentially targets activated CD4 T cells, expressing the major HIV receptor CD4, as well as the major chemokine coreceptors CCR5 and CXCR4. These coreceptors play a prominent role during HIV cell entrance phase, HIV transmission and also disease progression. They have been found to be differentially expressed by CD4 T cell subsets. Tuberculosis coinfection may enhance immune activation in vivo thus accelerating HIV disease progression and has become a major challenge in the control of TB in Africa. Introduction of HAART has reduced disease progression to AIDS, as well as risk of further morbidity and mortality. HAART results in a rapid decline of viral load and an initial increase of peripheral CD4 count, however little is known on the effect of HAART in regulation of coreceptor expression, immune activation status and CD4 T cell subset distribution in HIV infection and HIV/TB coinfection. This study is a cross-sectional analysis of coreceptor expression, immune activation status and CD4 T cell subpopulation distribution in South African HIV and HIV/TB coinfected patients before and after ARV. A total of 137 South African individuals were investigated, comprising 15 healthy normal donors (healthy subgroup), 10 patients with active pulmonary tuberculosis (PTB subgroup), 33 HIV-1 positive patients without active PTB (HIV subgroup), 23 positive patients with active PTB (HIV/PTB subgroup), 36 HIV-1 positive patients on ARV (HIV on ARV subgroup) and 20 HIV-1 positive patients with active PTB on ARV (HIV/PTB on ARV subgroup). CD4 absolute count and plasma viral load were determined for all donors. Freshly isolated PBMC were classified by flow cytometry into the following CD4+ T lymphocyte subsets: naïve (CD45+, CD27+), effector memory (CD45-, CD27-), central memory (CD45-, CD27+), and effector (CD45+, CD27-). Coreceptor expression and activation status was assessed by CCR5, CXCR4 and CD38 expression on CD4 T cell subsets. HIV, TB and HIV/TB coinfection was associated with a decrease in percentage CCR5+ T cells as compared to healthy controls, with the HIV/TB group showing the most extensive decrease. In treatment naive patients, CD4 T cells showed elevated surface expression of CCR5 and CD38 as determined by mean fluorescence intensity in HIV/TB co-infection compared to HIV infection alone. The percentage of antigen-experienced cells was higher in the HIV/TB co-infected group compared to the HIV group. The percentage of naïve T cells was decreased in both the HIV infected and the HIV/TB co-infected groups compared to healthy controls. HIV patients with more than 6 months of ARV showed decreased CCR5 and CD38 surface level expression in the HIV and the HIV/ TB co-infected subgroups. An increased percentage of naïve T cells was observed in the HIV infected subgroup, but not in the HIV/TB subgroup, similarly, a decreased percentage of antigen-experienced cells was observed in the HIV subgroup, but not in the HIV/TB co-infected subgroup. A positive correlation was found between CCR5 and CD38 expression, and CXCR4 and CD38 expression (Spearman coefficient of correlation respectively: r=0.59, p<0.001 and r=0.55, p<0.001). Furthermore we found plasma viral load positively associated with CD38 expression (r=0.31, p<0.001) and percentage activated CCR5+ expressing CD4 T cells positively related to viral load (r=0.31, p<0.001). Percentage naïve CD4 T cells was positively associated with CD4 count (r=0.60, p<0.001) and negatively correlated to viral load (r=-0.42, p<0.001). These results indicate that TB coinfection exacerbates certain aspects of dysregulation of CD4 T cell homeostasis and activation caused by HIV infection. In addition, ARV-associated decrease in coreceptor expression, immune activation status and a normalisation of CD4 T cell subset distribution was observed in HIV infected individuals, but not in HIV/TB coinfection. Despite viral suppression after ARV treatment, the decline in the immune activation marker CD38 and coreceptor CCR5 expression, increase in percentage naïve CD4 T cells and decrease of antigen-experienced cells did not reach the levels displayed in the healthy control group. This may indicate that ongoing (albeit reduced) T cell immune activation may occur in the presence of ARV. Further longitudinal studies are needed to closely monitor immune activation during ARV treatment. This study highlighted an association of TB disease with immune activation in HIV infection, the importance of T-cell activation in HIV pathogenesis and its impact on ARV treatment. Further studies are needed to identify causative factors that may lead to a persistent immune activation status during ARV treatment, and how TB coinfection confounds normal responses to ARV. / AFRIKAANSE OPSOMMING: In 2007 was ongeveer 2.1 miljoen sterftes wêreldwyd veroorsaak deur VIGS; ongeveer 70% in Sub-Sahara Afrika. CD4 T selle is die hoof teiken van MIV, aangesien dit die primêre CD4 reseptor, sowel as een of beide van die vernaamste chemokien koreseptore CCR5 en CXCR4 vrystel. Hierdie koreseptore speel ‘n prominente rol wanneer die MIV die sel binnedring, asook tydens MIV oordrag en verloop van die siekte. Dit word ook deur verskillende fraksies van CD4 T selle vrygestel. Gelyktydige TB infeksie mag immuunaktivering in vivo verhoog en dus die siekeproses versnel. MIV het ‘n groot uitdaging geword in die beheer van TB in Afrika. Bekendstelling van HAART het die ontwikkeling van VIGS vertraag, asook die risiko van verdere morbiditeit en mortaliteit. HAART veroorsaak ‘n vinnige afname in virale lading ‘n toename in CD4 telling, hoewel die spesifieke invloed van HAART op die regulering van koreseptor vrystelling, immuunaktivering en verspreiding van CD4 fraksies in MIV en MIV/TB infeksies nog onduidelik is. Hierdie studie het gepoog om koreseptor vrystelling, immuunaktiveringstatus en die verspreiding van CD4 subpopulasies in pasiënte met MIV en MIV/TB voor en na ARV behandeling te ondersoek. ‘n Totaal van 137 Suid-Afrikaanse individue is ondersoek en die studiegroep het bestaan uit 15 normale persone (gesonde subgroep), 10 pasiënte met aktiewe pulmonale TB (PTB subgroup), 33 MIV positiewe pasiënte sonder PTB (MIV subgroep), 23 MIV positiewe pasiënte met aktiewe PTB (MIV/PTB subgroep), 36 MIV positiewe pasiënte op ARV (MIV op ARV subgroep) en 20 MIV positiewe pasiënte met aktiewe PTB op ARV (MIV/PTB op ARV subgroep). Absolute CD4 telling en virale ladings was bepaal vir alle deelnemers. Vars geïsoleerde perifere bloed mononukleêre selle is geklassifiseer deur middel van vloeisitometrie as die volgende CD4 T limfosiet subgroepe: naïewe selle (CD45+, CD27+), effektor geheueselle (CD45-, CD27-), sentrale geheueselle (CD45-, CD27+), en effektor selle (CD45+, CD27-). Koreseptor vrystelling en aktivering was beoordeel volgens CCR5, CXCR4 en CD38 vrystelling op CD4 T sel subgroepe. HIV, TB en MIV/TB ko-infeksie is geassosieer met ‘n afname in die persentasie CCR5+ T selle, vergeleke met gesonde kontroles, waar die MIV/TB subgroep die grootste afname getoon het. In onbehandelde pasiënte het die CD4 T selle verhoogde vrystelling van CCR5 en CD38 op die oppervlakte getoon en dit is bevestig deur die gemiddelde fluoresserende vii intensiteit in die MIV/TB subgroep vergeleke met die subgroep met slegs MIV. Die MIV/TB subgroep het verder ook ‘n verhoogde persentasie totale geheue T selle getoon vergeleke met die MIV subgroep. Die persentasie naïewe T selle was egter verlaag in beide die MIV en MIV/TB subgroepe vergeleke met normale kontroles. MIV pasiënte wat langer as 6 maande op ARV behandeling was in beide die MIV en MIV/TB subgroepe, het ‘n verlaagde vrystelling van CCR5 en CD38 op die oppervlakte van die CD4 selle getoon. ‘n Verhoogde persentasie naïewe T selle het in die MIV subgroep voorgekom, maar nie in die MIV/TB subgroup nie. ‘n Soortgelyke tendens is gevind waar die persentasie totale geheueselle verlaag was in die MIV subgroep, maar nie in die MIV/TB subgroep nie. ‘n Positiewe korrelasie is gevind tussen CCR5 en CD38 vrystelling, asook CXCR4 en CD38 vrystelling (Spearman korrelasie koëffisiënt: r=0.59, p<0.001 en r=0.55, p<0.001 onderskeidelik). Verder het die plasma virale lading ‘n positiewe assosiasie getoon met CD38 vrystelling (r=0.31, p<0.001) en die persentasie geaktiveerde CCR5+ vrystellende CD4 T selle met virale lading (r=0.31, p<0.001). Die persentasie naïewe CD4 T selle het ‘n positiewe assosiasie getoon met CD4 telling (r=0.60, p<0.001) en ‘n negatiewe korrelasie met virale lading (r=-0.42, p<0.001). Volgens hierdie resultate vererger TB ko-infeksie sekere aspekte van die disregulasie van CD4 T selhomeostase en aktivering as gevolg van MIV infeksie. Verder kon ‘n ARVgeassosieerde afname in koreseptor vrystelling, immuunaktivering en normalisering van CD4 T sel fraksies bespeur word in die MIV subgroep, maar nie in die MIV/TB subgroep nie. Ten spyte van virale onderdrukking veroorsaak deur ARV behandeling, het die afname in die immuunmerker CD38 en koreseptor CCR5, toename in die persentasie naïewe CD4 selle en afname in totale geheue CD4 T selle nie die vlakke van die normale kontrolegroep bereik nie. Dit is moontlik dat volgehoue verlaagde T sel immuunaktivering nog steeds mag plaasvind in die teenwoordigheid van ARV. Verdere longitudinale studies is nodig om immuunaktivering tydens ARV behandeling te monitor. Hierdie studie het die belangrikheid van T sel aktivering in MIV patogenese en dit impak daarvan op ARV behandeling beklemtoon. Verdere studies is nodig om moontlike oorsake of bydraende faktore te identifiseer wat tot volgehoue immuunaktivering tydens ARV behandeling kan lei, asook tot mate waartoe TB ko-infeksie kan inmeng met die normale werking van ARV behandeling.

Amyloid beta (Aβ) has been postulated to be the principle initiator of the pathogenesis of Alzheimer’s disease (AD). Therefore, understanding the underlying mechanisms of Aβ induced neurotoxicity in the early stages of AD would be essential for finding potential therapeutic targets of AD. Aβ-binding alcohol dehydrogenase (ABAD) has been shown to be a mitochondrial binding site for Aβ. Expression of ABAD has been found to be increased in brains of AD sufferers. Two dimensional electrophoresis studies have revealed that endophilin 1 was upregulated in Tg mAPP/ABAD mice brains as compared to Tg mAPP, Tg ABAD and non-Tg mice brains. Increased expression of endophilin 1 has also been found in brains of AD patients as compared to non-demented control brain tissues. Endophilin1 has been reported to regulate c-Jun N-terminal kinase (JNK) activation. In this study, expression of dominant negative forms of endophilin 1 (DN-endophilin 1) in mouse cortical neurons exhibited a significant reduction of Aβ induced JNK activation. Furthermore, using cell counting methods, it was shown that the transfection of DN-endophilin 1 increased neuron survival after Aβ treatment. Aβ has also been proposed to disrupt the interaction of ABAD and Cyclophilin D (CypD), which would trigger mitochondrial permeable transition, thereby leading to neurotoxicity. For fluorescence resonance energy transfer (FRET) analysis of the interaction of ABAD and CypD, a mitochondria targeted, EYFP tagged ABAD plasmid (pMito-ABAD-EYFP) and an ECFP tagged CypD (pCypD-ECFP) plasmid were developed. Positive FRET signals in SK-N-SH cells co-expressing pMito-ABAD-EYFP and pCypD-ECFP indicated that ABAD interacts with CypD in the mitochondria of mammalian cells. RAGE (receptor for advanced glycation end products) has been reported to bind to Aβ and mediate the toxic effects of Aβ peptides on neurons and microglia. It has been shown previously that Tg mAPP/DN-RAGE mice display preserved cognitive function as compared to Tg mAPP mice. To investigate possible mechanisms involved in rescuing cognitive function by RAGE blockage, two dimensional electrophoresis was used to analyze differential protein expression between Tg mAPP and Tg mAPP/DN-RAGE mice cortex. Altered expression of four proteins, including NADH dehydrogenase flavoprotein 2 (NDUFV2), glyoxalase 1 (GLO1), proteasome subunit beta type 4 (PSMB4, or β7 subunit of proteasome) and nitrilase family, member 2 (Nit2) have been observed between Tg mAPP/DN-RAGE mice cortex and Tg mAPP mice cortex. NDUFV2 is a 24kDa subunit of complex 1 which is involved in ATP synthesis. GLO1 is a cytosolic enzyme that plays a role the glutathione-dependent detoxification of α-oxoaldehydes, such as methylglyoxal. PSMB4 is a subunit of the 26s proteosome which is in the degradation of ubiquitinylated proteins. The function of Nit2 is still unclear.

Receptor proteins on the surfaces of cells equip them to communicate with each other and to sense and interact with their environment. One receptor family, the αβ T-cell receptors (TCRs), allow T lymphocytes to detect and respond to pathogens via interactions with antigen-presenting major histocompatibility complex (MHC) molecules on target cells. A degree of TCR cross-reactivity (e.g. through structural similarity between peptide-MHC (pMHC) complexes) is essential to account for all possible pathogens, but can also lead to the misinterpretation of self antigens as foreign, and thereby elicit an autoimmune response, resulting in diseases such as multiple sclerosis (MS). Structural studies of pMHC and TCR-pMHC complexes have been key to developing of an understanding of the molecular basis of TCR cross reactivity, and the first strand of this thesis describes attempts to express and purify a highly cross-reactive MS patient-derived TCR for structural characterisation. The formation, purification and crystallisation of a TCR-self pMHC complex including another autoreactive TCR is also described. Another family of receptors, the fibronectin leucine-rich transmembrane proteins (FLRTs), has been implicated in roles in embryonic development including cell sorting and adhesion. In the second strand of this thesis, the nature of homotypic interactions between FLRTs, which may underlie adhesion between FLRT transfected cells, is investigated. Biophysical analyses demonstrate that these interactions may be mediated by the extracellular leucine-rich repeat (LRR) domain, and crystal structures of all three FLRT LRR domains suggest how interactions between them may underlie FLRT self-association at the cell surface. Residues which contribute to these interactions are conserved across different members of the FLRT family and different species. These findings confirm that FLRTs induce homotypic cell-cell adhesion, and suggest that this behaviour is mediated by self association at the cell surface via the LRR domain.

PTP69D is a receptor protein tyrosine phosphatase (RPTP) with two intracellular catalytic domains (Cat1 and Cat2), which has been shown to play a role in axon outgrowth and guidance of embryonic motorneurons, as well as targeting of photoreceptor neurons in the visual system of Drosophila melanogaster. Here, we characterized the developmental role of PTP69D in the giant fiber (GF) neurons; two interneurons in the central nervous system (CNS) that control the escape response of the fly. In addition to guidance and targeting functions, our studies reveal an additional role for PTP69D in synaptic terminal growth in the CNS. We found that inhibition of phosphatase activity in catalytic domain (Cat1) proximal to the transmembrane domain did not affect axon guidance or targeting but resulted in stunted terminal growth of the GFs. Cell autonomous rescue and knockdown experiments demonstrated a function for PTP69D in the GFs, but not its postsynaptic target neurons. In addition,complementation studies and structure-function analyses revealed that for GF terminal growth, Cat1 function of PTP69D requires the immunoglobulin and the Cat2 domain but not the fibronectin type III repeats nor the membrane proximal region. In contrast, the fibronectin type III repeats, but not the immunoglobulin domains, were previously shown to be essential for axon targeting of photoreceptor neurons. Thus, our studies uncover a novel role for PTP69D in synaptic terminal growth in the CNS that is mechanistically distinct from its function during earlier developmental processes. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2014. / FAU Electronic Theses and Dissertations Collection

Une compréhension fine et détaillée ciblant les mécanismes d’action de nouvelles molécules adjuvantes sur notre système immunitaire vise de manière directe à l’élaboration de nouveaux vaccins plus ciblés et plus efficaces, mais aussi à élargir nos connaissances quant à l’induction d’une réponse immune protectrice.<p>Au cours de cette thèse nous avons voulu comprendre les modes d’action de deux molécules lipidiques distinctes.<p>La première est le lipide cationique diC14-amidine dont il avait été démontré une action sur les cellules dendritiques en culture par une voie qui restait à élucider. Ce lipide cationique s'organise sous forme de liposomes en milieu aqueux et peut s'associer à de nombreux antigènes. La seconde est un analogue synthétique de l'adjuvant monophosphoryl lipide A (MPL), un dérivé du LPS, nommé CRX-527. À l'instar de sa molécule parente, le CRX-527 active le récepteur TLR4 et est considéré comme un adjuvant potentiel de vaccin ou comme immunostimulant isolé.<p>Au cours de notre travail, nous avons démontré que la diC14-amidine active les cellules cibles via le récepteur TLR4. En effet, l'absence de ce récepteur abolit les réponses induites par le lipide cationique diC14-amidine et la transfection du gène codant pour TLR4 rend répondeuses des cellules qui n'exprimaient pas ce récepteur. De plus, la diC14-amidine active et mature des cellules dendritiques, aussi bien de provenance murine qu'humaine, suggérant qu'elle puisse être utilisée en tant qu’adjuvant. Il avait d’ailleurs été précédemment décrit que l'injection d'un complexe diC14-amidine / allergène chez la souris induisait une réponse immune suffisante pour conférer une protection contre cet allergène. Dans ce contexte, nous avons caractérisé au niveau cellulaire la réponse induite suite à l'injection du complexe diC14-amidine / ovalbumine chez la souris. Cette réponse se manifeste par une production d'IFNγ lors d'une re-stimulation ex vivo par l'antigène OVA. <p>En ce qui concerne la molécule CRX-527, nous nous sommes particulièrement focalisés sur le rôle du co-récepteur du TLR4, le CD14, dans les réponses innées induites par le CRX-527. Nous avons établi que, de manière inattendue et contrairement à la plupart des ligands TLR4, le CRX-527 induit la production de nombreuses cytokines et chimiokines en complète absence de CD14, même à faible dose. De plus, l'ajout de CD14 sous sa forme soluble ne modifie pas le niveau des réponses associées à la voie de signalisation MyD88 / NF-κB. Cependant, il semblerait que la stimulation de cellules par du CRX-527 en présence de CD14 soluble recombinant, favorise plutôt la voie TRIF / IRF3, comme le suggère l'augmentation du taux de production d'IFNβ et d'activation d'IRF3. La molécule CD14 (membranaire et/ou soluble) ne serait donc pas qu'un simple transporteur de ligands, comme il l'a été décrit par le passé, mais bien une protéine impliquée dans la modulation des réponses induites lors de l'activation du TLR4. Le CD14 jouerait donc un rôle, aussi bien au niveau de la discrimination des ligands, que celle des voies de signalisation activées.<p> / Doctorat en Sciences agronomiques et ingénierie biologique / info:eu-repo/semantics/nonPublished

Introdução: O timo é um órgão linfóide especializado responsável por criar um microambiente propício para a diferenciação e maturação de células T. A quantificação dos níveis de TRECs (círculos excisados durante o rearranjo do TCR) vem sendo utilizada para avaliação e quantificação da função tímica em células do sangue periférico. Estudos que tenham realizado a quantificação dos níveis de TREC em crianças e adolescentes saudáveis brasileiros são escassos na literatura. Objetivo: No presente estudo, avaliamos os níveis de TREC em células mononucleares do sangue periférico associado à análise da expressão de linfócitos T CD3, CD4, CD8, de linfócitos T ativados co-expressando CD38 e HLA-DR e linfócitos T reguladores co-expressando CD25 e Foxp3 em crianças e adolescentes saudáveis em diferentes faixas etárias. Material e métodos: A quantificação dos níveis de sjTREC de DNA genômico em células mononucleares de sangue periférico foi realizada pelo método de PCR quantitativo em tempo real. A concentração de TREC foi expressa em número de cópias de TREC/?g de DNA. A análise da expressão dos marcadores CD3, CD4, CD8, CD38, HLA-DR, CD25 e Foxp3 foi realizada por citometria de fluxo. Resultados: Foram avaliadas 95 crianças e adolescentes, 46 do sexo feminino e 49 do sexo masculino com idades entre 1 e 18 anos. A média do número de cópias de TREC foi de 8,9 ± 3,6 x 104 TRECs/?g DNA. Não encontramos diferença significativa nos valores de TREC entre o sexo feminino e masculino (8,2 ± 3,3 x 104 TRECs/?g DNA vs 9,5 ± 3,9 x 104 TRECs/?g DNA, respectivamente, p = 0,085). Houve uma correlação inversa e significativa entre idade e os níveis de TREC (r = -0,846; p < 0,001), refletindo a já conhecida queda da função tímica com a idade. A expressão de CD3, CD4 e CD8 variou de 45 a 62%, 60 a 65% e 14 a 26%, respectivamente. Não houve correlação significativa entre a proporção de CD3, CD4 e CD8 e a idade dos indivíduos avaliados. Houve uma correlação inversa fraca entre os níveis de linfócitos T ativados expressando CD4+CD38+HLA-DR+ e idade (r = -0,286; p = 0,023), porém não encontramos correlação entre linfócitos T CD8+CD38+HLA-DR+ e idade (r = -0,229; p = 0,072). Houve uma correlação inversa entre os valores de linfócitos T expressando CD4+CD25+Foxp3+ e idade (r = -0,467; p = 0,04). Adicionalmente, encontramos correlação positiva entre a expressão de linfócitos T reguladores e o número de cópias de TREC/?g DNA (r = 0,529; p = 0,02). Conclusão: No presente estudo encontramos uma queda da função tímica com a idade, avaliada pela quantificação dos níveis de TREC em sangue periférico, que se correlacionaram positivamente com a proporção de células T reguladoras em crianças e adolescentes saudáveis. / Introduction: The thymus is a specialized lymphoid organ that is responsible for providing an exclusive microenvironment for T cell maturation and differentiation. The quantification of TREC (T cell receptor excision circle) has been widely used to evaluate and quantify thymic function in peripheral blood cells. Studies that evaluated TREC levels in Brazilian healthy children and adolescents are scarce in the literature. Objective: In the present study, we evaluated the TREC levels in peripheral mononuclear cells associated with the analysis of CD3, CD4, CD8 T cell markers, and activated T cells coexpressing CD38 and HLA-DR, and regulatory T cells co-expressing CD25 and Foxp3 in healthy children and adolescents in different age groups. Material and Methods: The quantification of sjTREC levels in genomic DNA of peripheral blood mononuclear cells (PBMC) was performed by real time quantitative PCR. TREC concentration was expressed as the number of copies of TREC/?g DNA. The analysis of CD3, CD4, CD8, CD38, HLA-DR, CD25 and Foxp3 expression was performed using flow cytometry methodology. Results: Ninety-five healthy children and adolescents were analyzed, 46 girls and 49 boys. The mean TREC count in PBMC in all individuals was 8.9 ± 3.6 x 104 TRECs/?g DNA. There was no significant difference in the number of TRECs/?g DNA between female and male gender (8.2 ± 3.3 x 104 TRECs/?g DNA vs 9.5 ± 3.9 x 104 TRECs/?g DNA, p = 0.085). There was an inverse correlation between age and TREC counts in PBMC in the 95 individuals (r = -0.846, p < 0.001), reflecting the well-known decrease of thymic function that occurs with age. The expression of CD3, CD4 and CD8 surface markers ranged between 45-62%, 60-65% and 14- 26%, respectively. There was no significant correlation between CD3, CD4 and CD8 proportion and age. There was a weak correlation between activated T cells expressing CD4+CD38+HLA-DR+ and age (r = -0.286; p = 0.023), however there was no significant correlation between T cells expressing CD8+CD38+HLA-DR+ and age (r = -0.229; p = 0.072). There was an inverse correlation between T cells expressing CD4+CD25+Foxp3+ and age (r = -0.467; p = 0.04). Additionally, we also found a positive correlation between CD4+CD25+Foxp3+ values and numbers of TREC/?g DNA in all studied individuals (r = 0.529, p = 0.02). Conclusion: In the present study we found a decrease in the thymic function with age, accessed by the quantification of the TREC level in peripheral blood, which was positively associated with the proportion of regulatory T cells.

Introdução: O timo é um órgão linfóide especializado responsável por criar um microambiente propício para a diferenciação e maturação de células T. A quantificação dos níveis de TRECs (círculos excisados durante o rearranjo do TCR) vem sendo utilizada para avaliação e quantificação da função tímica em células do sangue periférico. Estudos que tenham realizado a quantificação dos níveis de TREC em crianças e adolescentes saudáveis brasileiros são escassos na literatura. Objetivo: No presente estudo, avaliamos os níveis de TREC em células mononucleares do sangue periférico associado à análise da expressão de linfócitos T CD3, CD4, CD8, de linfócitos T ativados co-expressando CD38 e HLA-DR e linfócitos T reguladores co-expressando CD25 e Foxp3 em crianças e adolescentes saudáveis em diferentes faixas etárias. Material e métodos: A quantificação dos níveis de sjTREC de DNA genômico em células mononucleares de sangue periférico foi realizada pelo método de PCR quantitativo em tempo real. A concentração de TREC foi expressa em número de cópias de TREC/?g de DNA. A análise da expressão dos marcadores CD3, CD4, CD8, CD38, HLA-DR, CD25 e Foxp3 foi realizada por citometria de fluxo. Resultados: Foram avaliadas 95 crianças e adolescentes, 46 do sexo feminino e 49 do sexo masculino com idades entre 1 e 18 anos. A média do número de cópias de TREC foi de 8,9 ± 3,6 x 104 TRECs/?g DNA. Não encontramos diferença significativa nos valores de TREC entre o sexo feminino e masculino (8,2 ± 3,3 x 104 TRECs/?g DNA vs 9,5 ± 3,9 x 104 TRECs/?g DNA, respectivamente, p = 0,085). Houve uma correlação inversa e significativa entre idade e os níveis de TREC (r = -0,846; p < 0,001), refletindo a já conhecida queda da função tímica com a idade. A expressão de CD3, CD4 e CD8 variou de 45 a 62%, 60 a 65% e 14 a 26%, respectivamente. Não houve correlação significativa entre a proporção de CD3, CD4 e CD8 e a idade dos indivíduos avaliados. Houve uma correlação inversa fraca entre os níveis de linfócitos T ativados expressando CD4+CD38+HLA-DR+ e idade (r = -0,286; p = 0,023), porém não encontramos correlação entre linfócitos T CD8+CD38+HLA-DR+ e idade (r = -0,229; p = 0,072). Houve uma correlação inversa entre os valores de linfócitos T expressando CD4+CD25+Foxp3+ e idade (r = -0,467; p = 0,04). Adicionalmente, encontramos correlação positiva entre a expressão de linfócitos T reguladores e o número de cópias de TREC/?g DNA (r = 0,529; p = 0,02). Conclusão: No presente estudo encontramos uma queda da função tímica com a idade, avaliada pela quantificação dos níveis de TREC em sangue periférico, que se correlacionaram positivamente com a proporção de células T reguladoras em crianças e adolescentes saudáveis. / Introduction: The thymus is a specialized lymphoid organ that is responsible for providing an exclusive microenvironment for T cell maturation and differentiation. The quantification of TREC (T cell receptor excision circle) has been widely used to evaluate and quantify thymic function in peripheral blood cells. Studies that evaluated TREC levels in Brazilian healthy children and adolescents are scarce in the literature. Objective: In the present study, we evaluated the TREC levels in peripheral mononuclear cells associated with the analysis of CD3, CD4, CD8 T cell markers, and activated T cells coexpressing CD38 and HLA-DR, and regulatory T cells co-expressing CD25 and Foxp3 in healthy children and adolescents in different age groups. Material and Methods: The quantification of sjTREC levels in genomic DNA of peripheral blood mononuclear cells (PBMC) was performed by real time quantitative PCR. TREC concentration was expressed as the number of copies of TREC/?g DNA. The analysis of CD3, CD4, CD8, CD38, HLA-DR, CD25 and Foxp3 expression was performed using flow cytometry methodology. Results: Ninety-five healthy children and adolescents were analyzed, 46 girls and 49 boys. The mean TREC count in PBMC in all individuals was 8.9 ± 3.6 x 104 TRECs/?g DNA. There was no significant difference in the number of TRECs/?g DNA between female and male gender (8.2 ± 3.3 x 104 TRECs/?g DNA vs 9.5 ± 3.9 x 104 TRECs/?g DNA, p = 0.085). There was an inverse correlation between age and TREC counts in PBMC in the 95 individuals (r = -0.846, p < 0.001), reflecting the well-known decrease of thymic function that occurs with age. The expression of CD3, CD4 and CD8 surface markers ranged between 45-62%, 60-65% and 14- 26%, respectively. There was no significant correlation between CD3, CD4 and CD8 proportion and age. There was a weak correlation between activated T cells expressing CD4+CD38+HLA-DR+ and age (r = -0.286; p = 0.023), however there was no significant correlation between T cells expressing CD8+CD38+HLA-DR+ and age (r = -0.229; p = 0.072). There was an inverse correlation between T cells expressing CD4+CD25+Foxp3+ and age (r = -0.467; p = 0.04). Additionally, we also found a positive correlation between CD4+CD25+Foxp3+ values and numbers of TREC/?g DNA in all studied individuals (r = 0.529, p = 0.02). Conclusion: In the present study we found a decrease in the thymic function with age, accessed by the quantification of the TREC level in peripheral blood, which was positively associated with the proportion of regulatory T cells.

In chronic lymphocytic leukemia (CLL), the presence of multiple subsets expressing ‘stereotyped’ B-cell receptors (BCRs) has implicated antigen(s) in leukemogenesis. These stereotyped subsets display similar immunoglobulin (IG) gene usage, almost identical complementarity determining region 3’s and may share clinical features. For instance, subsets #1 (IGHV1/5/7/IGKV1-39) and #2 (IGHV3-21/IGLV3-21) have inferior outcome compared to non-subset patients, whereas subset #4 (IGHV4-34/IGKV2-30) display a favourable prognosis. The aim of this thesis was to investigate genomic aberrations, gene expression patterns and methylation profiles in stereotyped subsets and compare epigenetic profiles in CLL and mantle cell lymphoma (MCL). In paper I, we investigated genomic aberrations in subsets #2, #4 and #16 and in non-stereotyped samples (n=101) using high-density 250K SNP arrays. Subset #2 and non-subset #2 IGHV3-21 cases displayed a higher frequency of aberrations than subset #4 cases. The high incidence of del(11q) in both subset #2/non-subset #2 may reflect the adverse survival reported for IGHV3-21 patients. In contrast, the lower frequency of genetic events and lack of poor-prognostic aberrations in subset #4 may partially explain their indolent disease. In paper II, we analysed the global RNA expression in subset #4, #16 and non-subset IGHV4-34 CLL patients (n=25). Subsets #4 and 16 showed distinct gene expression profiles, where genes involved in cell regulatory pathways were significantly lower expressed in subset #4, in line with their low-proliferative disease. In paper III, a genome-wide methylation array was applied to investigate methylation profiles in subsets #1, #2 and #4 (n=39). We identified differential methylation patterns for all subsets and found affected genes to be involved in e.g. apoptosis and therapy resistance. When performing functional annotation, a clear enrichment of genes involved in adaptive immunity was observed. These genes were preferentially methylated in subset #1 when compared to either subset #2 or #4, possibly due to different antigen responses. In paper IV, the genome-wide methylation profiles for 30 CLL and 20 MCL patients were investigated. Distinct methylation profiles were observed, where MCL displayed a more homogeneous profile. Homeobox transcription factor genes showed a higher degree of methylation in MCL, while apoptosis-related genes and proliferation-associated genes were methylated in CLL. In summary, this thesis demonstrates that stereotyped CLL subsets display differences in gene expression profiles, genetic aberrations and methylation patterns, underscoring the functional relevance of subgrouping according to BCR stereotypy. The distinct methylation profiles of CLL and MCL suggests that different epigenetic mechanisms are involved in the pathogenesis of these B-cell malignancies.

This work is centered on the study of the NKG2 C-type lectin-like receptors on NK and CD4+T cells. We provide evidence supporting that CD4+T cells specific for Human Cytomegalovirus (HCMV) may express different NK cell receptors, and demonstrate that the C-type lectin-like receptor NKG2D is expressed on cytotoxic CD4+T cells with an effector/memory phenotype, enhancing their TCR-dependent proliferation and cytokine production. A second part of the work is centered on the study of the CD94/NKG2 receptors on NK cells. We show that NKG2A can be induced on NKG2C+ NK cells upon activation with rIL-12 or when cocultured with HCMV-infected dendritic cells, and that NKG2A expression inhibits the response of NKG2C+NK clones against HLA-E-expressing targets, providing a potential regulatory feedback mechanism to control cell activation. Altogether, our results support that expression of NKG2 C-type lectin like receptors may be shaped during the course of viral infections, providing mechanisms to finely regulate both NK and CD4+T cell functions. / Aquesta tesi es centra en l'estudi dels receptors lectina de tipus C NKG2 en cèl·lules Natural Killer i T CD4+. Demostrem que les cèl·lules T CD4+ específiques pel Cytomegalovirus Humà poden expressar diferents receptors NK, i que el receptor lectina tipus C NKG2D s'expressa en cèl·lules citotòxiques i de memòria, potenciant la proliferació i secreció de citocines depenent del TCR. La segona part d'aquesta tesi es centra en l'estudi de l'expressió dels receptors CD94/NKG2 en cèl·lules NK. Mostrem com l'expressió de CD94/NKG2A s'indueix en cèl·lules CD94/NKG2C+ estimulades amb IL-12 o cultivades amb cèl·lules dendrítiques infectades pel Cytomegalovirus Humà, i que l'expressió de CD94/NKG2A inhibeix la resposta de clons NK CD94/NKG2C+ envers dianes HLA-E+, constituint un possible mecanisme de feedback negatiu per controlar l'activació cel·lular. En resum, els nostres resultats demostren que l'expressió dels receptors lectina tipus C NKG2 pot ser modificada durant les infeccions víriques consitutint un possible mecanisme per regular la resposta tant de cèl·lules NK com T CD4+.

Low affinity Fcg receptor III (FcgRIII, CD16) triggers a variety of cellular events upon binding to the Fc portion of IgG. A real-time flow cytometry method was developed to measure the affinity and kinetics of such low affinity receptor/ligand interactions, which was shown as an easily operated yet powerful tool. Results revealed an unusual temperature dependence of reverse rate of CD16aTM dissociating from IgG. Except for a few studies using mammalian cell CD16s, most kinetics analyses use purified aglycosylated extracellular portion of the molecules, making it impossible to assess the importance of the receptor anchor and glycosylation on ligand binding. We used a micropipette adhesion frequency assay to demonstrate that the anchor length affects the forward rate and affinity of CD16s for IgG in a species specific manner, most likely through conformational changes. Receptor glycosylation dramatically reduced ligand binding by 100 folds. T cell receptor (TCR) is arguably the most important receptor in the adaptive human immune system. Together with coreceptor CD4 or CD8, TCR can discriminate different antigen peptides complexed with major histocompatibility complex (MHC) molecule (pMHC), which differ by as few as only one amino acid, and trigger different T cell responses. When T cell signaling was suppressed, TCR had similar affinity and kinetics for agonist and antagonist pMHC whose binding to CD8 was undetectable. TCR on activated T cell had a higher affinity for pMHCs, suggesting that TCRs organize themselves differently on activated T cells than on naïve T cells. In the absence of inhibitors for signaling, TCR binds agonist pMHC with several orders of magnitude higher affinity than antagonist pMHC. In addition, engagement of TCR by pMHC signals an upregulation of CD8 binding to pMHC, which is much stronger than the TCR-pMHC binding. The transition from weak TCR binding to the strong CD8 binding takes place around 0.75 second after TCR in contact with pMHC and can be reduced by several inhibitors of tyrosine and lipid phosphorylation, membrane rafts, and actin cytoskeleton. These results provide new insights to understanding T cell discrimination.